Scientists agree that the Big Bang Theory is currently the best explanation for the beginning of the universe. It states that all the matter and radiation of the universe was located in a dense smaller singularity. An explosion and then an expansion occurred and that expansion is currently going on still. It has been calculated that the Big Bang occurred approximately 14.5 billion years ago. Evidence to support this is cosmic background radiation which was discovered in the 1960's which is evidence that this event occurred as it is leftover radiation from this event. Also, galaxies are moving apart and the most distant are moving faster. The universe is like raisin bread that is baking, each raisin in the bread moves apart from all others, with no center to the universe. The raisins of course, are the galaxies in the universe. There is the red shift that occurs when energy is coming from an object moving away, just like our galaxies. However, no one knows exactly what occurred, this is just the best theory currently to explain things.